No, cavemen were very egalitarian. This is because back then, you couldn't hoard much of anything - food spoils quickly, sex requires your partner to like you, and personal possessions were things like tools or the odd bit of clothing. It was when wealth could be preserved, such as livestock, stored grain, jewelry, and eventually coinage, that wealth became an hereditary thing.

This is why a future economic system has to be designed to prevent the excessive hoarding of wealth. Not too little, nor too much. Humans weren't evolved to be free of consequence, especially from each other.

If you ran humanity in thousands of simulations how often would we end up in the same capitalistic situation?

No, but greed and envy is. That's why humans have written so much in the last thousand years about greed and envy.

It's right there on Karl Marcos' "All About Capital", basic economics commie

What "possibly impossible starting point" does Communism rely on? This reads like someone that hasn't actually attempted to engage with what Communists believe, to be honest.

Yeah I think you hit the nail on the head here. It's interesting to think about how even though communism could theoretically be the best system, it could mean nothing if we don't know how to meet the conditions to achieve it in the first place.